The present invention relates to an air-conditioning system for vehicles, in particular passenger cars.
In a known air-conditioning system of this type (W. Frank and H.-D. Oe.beta. "Mehr Klimakomfort im Personenwagen" [More Climatic Comfort in the Passenger Car], special publication from ATZ, Automobiltechnische Zeitschrift [Automotive Journal] No. 9/1987, p. 4, FIG. 2), temperature-controlled air is fed to the central plane of the passenger compartment by a central jet arranged in the dashboard in a so-called reheat operation. In a reheat operation, the air taken in is first cooled by the evaporator and thus dehumidified and then heated to the desired temperature in the heat exchanger. The air quantity fed to the passenger compartment is controlled by a shut-off flap at the air outlet opening for the central jet, which shut-off flap throttles the air flow to a greater or lesser extent, dependent on its position. In the operation mode "maximum cooling", cold air is additionally drawn off via the cold-air flap, also called the draw-off flap, from the space downstream of the evaporator or upstream of the heat exchanger, and fed to the passenger compartment via the air duct. In contrast, in heating operation, the air outlet is shut off via the central jet since the air--by virtue of the concept--is either too cold (less than approx. 5.degree. C.) or very hot (more than 40.degree. C.).
In a further air-conditioned system know from the same literature reference (p. 5, illustration 5), the hot-air flap has been omitted and the cold-air flap has the function of an air-mixing flap, by means of which cold air is mixed in with the hot air flowing into the air duct from the hot-air opening in order to achieve the desired air temperature. By a shut-off valve at the air outlet opening for the central jet, the desired air quantity is, in turn, set infinitely variably by lesser or greater throttling. In this air-conditioning system, various pressure conditions can arise in the air-conditioning box due to the throttling of the mixed air at the air outlet opening of the central jet, thereby leading to reverse flows; that is, cold air in the direction downstream of the heat exchanger, with the result that then undesirably cold air also issues from the air outlet openings located downstream of the heat exchanger for defroster, lateral and foot-room jets. This can only be avoided by additional return flaps at the cold-air and hot-air openings.
The object of the present invention is to provide an improved air-conditioning system in which temperature control and metering of the air issuing from the central jet is possible with relatively small construction expenditure.
This object is achieved in the air-conditioning system according to the invention, by a departure from the principle generally used in air-conditioning systems of temperature control by mixed-air flaps and quantity regulation by a shut-off flap. Instead, each bypass opening (hot-air and cold-air openings) is throttled individually. Since no further shut-off flap is arranged downstream of the bypass flaps for the bypass openings in the air flow direction, in all modes of operation only a single flow results in the direction of the passenger compartment. Return flaps, as in the air-conditioning system described above, therefore are unnecessary. The actuators for the bypass flaps are infinitely variable. Vacuum elements with a feedback potentiometer or electric stepping motors can be used as actuators.
A further advantage of the air-conditioning system according to the invention also lies in the reduction of noise as the bypass flaps are located relatively remotely from the central jet.
If a capability for separate setting of the air-conditioning on the driver's side of the passenger side in the passenger compartment is desired (right/left separation), separate bypass flaps for two separate central jets, that is to say a total of four bypass flaps, must be provided. In the know air-conditioning system described above, in the case of a right/left separation, a total of two mixed-air and four return flaps as well as two shut-off flaps for the quantity control would be required, which means that, in the case of the air-conditioning system according to the invention, a considerable savings of costs can be achieved with the same comfort.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.